Self-adjusting socket wrench



Sept. 25, 1956 M. R. LEIBOWITZ SELF-ADJUSTING SOCKET WRENCH Filed ma 4, 1955 States Patent ()fiice SELF-ADJUSTIN G SOCKET WRENCH Michael R. Leibowitz, Brooklyn, N. Y.

Application May 4, 1955, Serial N 0. $05,910

t Claims. (Cl. 81-91) My invention relates to a mechanism for tightening and removing nuts and bolts by a gripping device, such gripping device fitting over the nut or bolt and being self-adjusting.

There are many cases of nut and bolt adjustment in which a socket type wrench is most efficacious. However, the frequent changing of sockets, and the potential loss of one of the many sockets making up a set impose an inconvenience upon the mechanic.

It is an object of this invention to produce a socket wrench having pivotally mounted gripping arms, each arm being spring-pressed to its work-gripping position and contacted by a rotating Wedge, which because of its resemblance to clover leaves I will term a clover wedge.

The gripping faces of the arms may have grooves cut or forged in them to better accommodate the nuts or bolts they grip. The grooves would be 120 for hexagonal nuts in a three jaw wrench or 90 for square nuts in either a two or four-jaw wrench. The grooves serve another purpose as well, since they increase the size of the opening when the arms are in their normal closed position, so that the arms may be spread more easily over a nut or bolt by a simple downward pressure.

In using this wrench to remove a nut the arms are pushed over the top and sides of the nut. the corners of the nut being located in the accommodating grooves. Rotation of the clover wedge first causes wedging of the arms in their gripping positions, after which the entire device rotates as a unit. To apply a nut to a hardto-reach stud, the nut would first be inserted into the socket formed by the arms where it would be held by spring pressure, the device and the nut then being transported as a unit to the location of the stud.

Referring to the drawings:

Fig. 1 is a plan view of Fig. 2, but shows a hexagonal nut gripped by three pivotally mounted arms, which are wedged in their nut-gripping positions by spiral surfaces of a clover wedge;

Fig. 2 is a side elevation of the apparatus showing the nut-gripping ends of the arms in their outermost positions, a fulcrum block being shown in section, and the dotted lines showing the arms in position for gripping the nut shown in Fig. 1;

Fig. 3 shows the clover wedge and arms in a partly schematic inverted plan view, the dotted circles representing the rear ends of the arms in the dotted line positions of Fig. 2; Fig. 3 also shows a vector diagram illustrating the components of the wedging force.

Fig. 4 shows an arm of the clover wedge in a fragmentary plan view that is cut by section planes 5-5, 6-6, 7-7 to show the varying cross section of the arm;

Fig. 5 is a vertical section through a longitudinal axis of symmetry of one arm of the clover wedge, and is taken along the line 55 in Fig. 4;

Fig. 6 is a vertical transverse section taken along the line 6-6 in Fig. 4;

gripping action of elongate levered arms 2 induced by leverage applied from behind coplanar fulcrum axes of the arms 2. The levered arms 2 have intermediate portions provided with transverse bores and are pivotally mounted in peripheral grooves 11 in a fulcrum member 5 by fulcrum pins 6 which extend through said trans-- verse bores and through coaxial transverse holes 9 in the fulcrum member 5, the holes 9 communicating with the slots 11. The pin 6 fits freely through the arm 2 but tightly in the hole 9. It may be threaded at one end or riveted, or force-fitted in hole 9. The arms are equipped on the gripping ends with grooves 8 to better accommodate a nut. Since the illustration shows a three-armed wrench for hexagonal nuts the grooves 8 are made so that they form angles of 120, but for square nuts the angle would be and there would be two or four arms. rounded at their rear ends to accommodate better to a clover wedge 1, and are disposed in notches formed by the intersecting spiral surfaces of the wedge.

The clover wedge 1 contains a drive hole 4 in which i a handle is attachable. The clover wedge 1 is permanently attached to, or made integral with, a cylindrical rod 3 which, at its forward end, extends axially through a round hole 13 in the fulcrum member 5. Fulcrum member 5 is positioned on the rod 3 by split rings 7 which fit into annular grooves in the rod 3.. arms 2 are biased by a spring assembly 12 consisting of a spring and rivet which is force-fitted into each of the arms 2. The spring at its point of contact with the rod 3 might be concave to better accommodate the bar.

In observing schematic Figure 3 it will be seen that the force imparted upon each arm 2 by the appropriate spiral surfaces of each notch in the clover wedge 1 can be broken into two vectors. One of these vectors goes radially outward, this is the levering force which contracts the jaws on the other side of the fulcrum. other vector is a torque vector at right angles to the first in the direction of rotation. The relative magnitude of these vectors is determined by the angle made by the radius vector from the center of the clover wedge (which would lie at the center of the drive hole 4) and the tangent at the contact point of the arm 2 and the spiral surface of the clover wedge 1. If the torque vector supersedes the radial vector by too great a magnitude the wrench will turn more than it will grip with consequent slipping on the fastening.

To find the shape for the wedges such that the relative magnitude of the two vectors be constant at all points of contact on the wedge; we must find a curve such that its radius vector from the origin to each point on the curve makes a constant angle with the tangent at that point. Setting up these conditions in a differential equation in polar coordinates and solving we get:

where p is the radius vector, e the base of the natural logarithms, k the tangent value of the constant angle, 0 the constant of integration determining the size of the curve, and where 0 represents the angle of rotation of the radius vector p from the zero line through the origin. If we want to have the two vectors equal we must make Patented Sept. 25, 1956 The clover-wedge ends of the arms 2 are' The levered The l the constant angle between the radius vector and the tangent equal to 45, in which case k will equal 1 so:

Each leaf of the clover wedge would then have wedging surfaces defined by a section of a logarithmic spiral on each side of its axis of symmetry, both spiral segments meeting at the outer end of the leaf, and intersecting, at their inner ends, the spiral segments of adjacent leaves to form the previously mentioned arm receiving notches. However various other shapes might also prove eificacious.

In Figures 4 through 7 it will be observed that the angle of slope between the wedging surface and the rear surface of the fiat and parallel surfaces of each leaf of the clover wedge also varies. The further from the center the more acute becomes the angle of slope with respect to the rearflat surface. This is done to better accommodate the arm 2 in its different positions along the spiral of the wedging surface as shown in Figure 2. To do this most effectively the angle of slope between the wedging surface and a perpendicular to the flat surface should be made equal to are cos.d/ h

where d is the distance along the perpendicular from the front surface of the clover wedge 1 to the fulcrum axis of the pin 6, and h is the distance along the arm 2 from the fulcrum axis of the pin 6 to the point of contact with the wedge 1.

' In Figure 1 a nut 10 is shown as being held 1n the I claim: 1. A self-adjusting socket wrench comprising elongate gripping arms, a fulcrum member to which each of said arms is pivoted on a transverse axis intermediate the length of the arm, a wedge mounted on said fulcrum member for rotation about an axis extending perpendicularly to a plane containing said transverse axes, said wedge having a plurality of notches formed by the intersection of spiral surfaces, rear portions of said arms being disposed in said notches, and means continually biasing forward portions of said arms toward their work-gripping positions, whereby rotation of said Wedge in either direction first causes said spiral surfaces to contact said rear portions of said arms to wedge said arms in their work-gripping positions and then causes the entire wrench to rotate as a unit.

2. A self-adjusting socket wrench as recited in claim 1, wherein the rotating wedge is mounted on said fulcrum member by means of a rod extending from a forward surface of the wedge, said rod being journaled in a bore in said fulcrum member.

3. A self-adjusting socket wrench as recited in claim 1, wherein the spiral surfaces of the rotating wedge form a clover-leaf design, the spiral surfaces between adjacent notches being made symmetrical about a central axis whereby the spiral surfaces exert similar pressure when the wedge is rotated in either direction.

4. A self-adjusting socket wrench as recited in claim 1, wherein the spiral surfaces of each notch conform to the formula in polar coordinates, in other words a logarithmic spiral or a curve approximating a logarithmic spiral.

References Cited'in the file of this patent UNITED STATES PATENTS 86,181. Samuel Jan. 26, 1869 289,506 Davidson Dec. 4, 1883 356,540; Joel Jan. 25, 1887 445,258 Cram Jan. 27, 1891 627,669 Jenkins June 27, 1899 925,745 Booth June 22, 1909 1,357,935 Argetsinger Nov. 9, 1920 1,408,275 Eckles Feb. 28, 1922 1,649,567 Bruckmann Nov. 15, 1927 2,478,996 Alexander Aug. 16, 1949 

